Manipulando Null em SQL Dinâmico

Estou tentando capturar o valor CDC existente e desabilitar e habilitar novamente para truncamento de partição. Não consegui descobrir como lidar com valores nulos em SQL dinâmico.

Se eu passar diretamente @role_name =NULL, & @filegroup_name = NULL. Está funcionando bem.

-- Enable cdc for that table
    declare @cmd_cdc_enable nvarchar(max)
    SET @cmd_cdc_enable =N'
    exec sys.sp_cdc_enable_table 
    @source_schema = '''+@v_source_schema+''', 
    @source_name = '''+@v_source_table+''',
    @capture_instance = '''+@v_capture_instance +''',
    @supports_net_changes = 1,
    @role_name     =NULL,
    @filegroup_name = NULL,
    @allow_partition_switch = 1

Código de exemplo:

GO
EXEC sys.sp_cdc_enable_db
GO


create schema [C1810429]
go


create table [C1810429].[STYTOTAL_RAW_NEW] (ID int identity primary key, name varchar(200))

-- Enable First time
go
EXEC sys.sp_cdc_enable_table  
    @source_schema = N'C1810429',  
    @source_name   = N'STYTOTAL_RAW_NEW', 
    @capture_instance = 'C1810429_STYTOTAL_RAW_NEW',
    @supports_net_changes = 1 ,
    @role_name     = NULL,  
    @filegroup_name = NULL, 
    @allow_partition_switch = 1



drop table if exists tbl_sp_cdc_help_change_data_capture

create table tbl_sp_cdc_help_change_data_capture (
source_schema sysname null, source_table sysname null,  capture_instance sysname null,  object_id int null, source_object_id int null,  
start_lsn binary(10) null,  end_lsn binary(10) null, supports_net_changes bit null,has_drop_pending bit null,   role_name sysname null, 
index_name sysname null,    filegroup_name sysname null,    create_date datetime null,  index_column_list nvarchar(max) null,   captured_column_list nvarchar(max) null
)

insert into tbl_sp_cdc_help_change_data_capture
Exec sys.sp_cdc_help_change_data_capture @source_schema='C1810429',@source_name='STYTOTAL_RAW_NEW'

-- select * from tbl_sp_cdc_help_change_data_capture



    declare @v_source_schema sysname
    declare @v_source_table sysname 
    declare @v_capture_instance sysname
    declare @v_supports_net_changes int
    declare @v_role_name sysname
    declare @v_filegroup_name sysname

    select @v_source_schema=source_schema,@v_source_table=source_table,@v_capture_instance=capture_instance,@v_supports_net_changes=supports_net_changes,
    @v_role_name=role_name,@v_filegroup_name=[filegroup_name]
    from tbl_sp_cdc_help_change_data_capture

    --select @v_source_schema,@v_source_table,@v_capture_instance,@v_supports_net_changes,@v_role_name,@v_filegroup_name

    /*
    -- disable cdc for that table
    declare @cmd_CDC_disable nvarchar(max)
    SET @cmd_CDC_disable =N'
    exec sys.sp_cdc_disable_table 
    @source_schema = '''+@v_source_schema+''', 
    @source_name = '''+@v_source_table+''',
    @capture_instance = '''+@v_capture_instance+'''

    '
    --print @cmd_CDC_disable
    EXEC sys.sp_executesql @cmd_CDC_disable

    select 'Disabled'

    */
    

    --select @v_source_schema,@v_source_table,@v_capture_instance,@v_supports_net_changes,@v_role_name,@v_filegroup_name

    -- Enable cdc for that table
    declare @cmd_cdc_enable nvarchar(max)
    SET @cmd_cdc_enable =N'
    exec sys.sp_cdc_enable_table 
    @source_schema = '''+@v_source_schema+''', 
    @source_name = '''+@v_source_table+''',
    @capture_instance = '''+@v_capture_instance +''',
    @supports_net_changes = 1,
    @role_name     ='''+@v_role_name  +''',
    @filegroup_name = '''+@v_filegroup_name  +''',
    @allow_partition_switch = 1

    '
    print @cmd_cdc_enable

    EXEC sys.sp_executesql @cmd_cdc_enable

    --select 'Enabled'